Method and apparatus for improving call quality of hands-free call device, and hands-free call device

ABSTRACT

The present invention discloses a method and an apparatus for improving the call quality of a hands-free call device, and a hands-free call device. The hands-free call device comprises a transmitter end composed of a main microphone and at least one auxiliary microphone. The method comprises: scanning within an initial first collection angle of a transmitter end; after a voice feature signal is scanned within the first collection angle, according to a direction of the voice feature signal, determining a second collection angle smaller than the first collection angle within the first collection angle; and calibrating the transmitter end to a direction determined by the second collection angle. In this method, voice pickup is conducted using a relatively small voice protection angle, so that the interference from ambient noise can be greatly reduced, to achieve the purpose of improving the transmission signal to noise ratio, thus the directivity of a voice in a hands-free call device during a call is more clear, which improves the call quality.

FIELD OF THE INVENTION

The present invention relates to the field of hands-free call devices,and particularly, to a method and an apparatus for improving the callquality of a hands-free call device, and a hands-free call device.

BACKGROUND OF THE INVENTION

Hands-free call devices in the prior art, such as smart wrist-wearingdevices like smart watch and smart band, usually use a rather largevoice protection angle under the hands-free call mode since the positionof the smart watch relative to a user's mouth is uncertain, thus muchambient noise is collected during the voice pickup, and the transmissionsignal to noise ratio is influenced. Meanwhile, sound from theloudspeaker of the hands-free call device such as the smart watch willbe heard by not only the caller himself, but also other people nearby,and the private information can be easily leaked. In conclusion, theabove defects of the transmitter end and the receiver end lead to not sohigh a call quality of the hands-free call device in the prior art.

SUMMARY OF THE INVENTION

The present invention provides a method and an apparatus for improvingthe call quality of a hands-free call device, and a hands-free calldevice, so as to solve the problem that much ambient noise is collectedand the transmission signal to noise ratio is low during a call of thehands-free call device.

According to one aspect of the present invention, a method for improvingthe call quality of a hands-free call device is provided, wherein thehands-free call device comprises a transmitter end composed of a mainmicrophone and at least one auxiliary microphone, and the methodcomprises:

scanning within an initial first collection angle of the transmitterend;

after a voice feature signal is scanned within the first collectionangle, according to a direction of the voice feature signal, determininga second collection angle smaller than the first collection angle withinthe first collection angle; and

calibrating the transmitter end to a direction determined by the secondcollection angle.

Wherein, after a voice feature signal is scanned within the firstcollection angle, according to a direction of the voice feature signal,determining a second collection angle smaller than the first collectionangle within the first collection angle comprises:

making a reverse extension line through the main microphone in directionγ1 when a voice feature signal is scanned in direction γ1 within theinitial first collection angle of the transmitter end, drawing a circleby taking the main microphone as a center and a connection line betweenthe main microphone and one of the auxiliary microphones as a radius,and determining intersection of an arc of the circle and the reverseextension line as a virtual microphone of the main microphone;

taking the main microphone and its virtual microphone as a new voicearray, defining an angle β1 smaller than the first collection angle, andjudging in real time whether a voice feature signal is existed withinthe angle β1; if so, determining the angle β1 as a second collectionangle; and

if not, taking the connection line between the main microphone and oneof the auxiliary microphones as an axis of symmetry, defining a mirrorangle β2 of the angle β1 with respect to the axis of symmetry, anddetermining the angle β2 as a second collection angle.

Wherein, judging in real time whether a voice feature signal is existedwithin the angle β1 comprises:

detecting envelope energy of the voice feature signal in direction γ1,and detecting a zero-crossing rate of the voice feature signal indirection γ1 when an energy detection value is larger than a firstpredetermined threshold; and

determining that a voice feature signal is existed in the angle β1, whenthe zero-crossing rate of the voice feature signal in direction γ1reaches a second predetermined threshold.

Wherein, detecting envelope energy of the voice feature signal indirection γ1 comprises:

detecting envelope energy through the following formula:

power=0;power=power*(1-alpha)+Σ_(n=1) ^(N) x(n)*x(n)

wherein, power is an energy value of the voice feature signal, parameteralpha is a weighted factor, and parameter N is a specific value of voicefeature signal at a time point;

detecting a zero-crossing rate of the voice feature signal in directionγ1 comprises: detecting a zero-crossing rate through the followingformula:

${Z\_ rate} = \left. {\frac{1}{2}\sum\limits_{m = 0}^{N - 1}}\; \middle| {{sgn}\left\lbrack {{x(n)} - {{sgn}\left( {x\left( {n - 1} \right)} \right)}} \right\rbrack} \right.$

wherein, Z_rate is a zero-crossing rate of the voice feature signal, nis a value among a discrete time series, and

${{sgn}\lbrack x\rbrack} = {\begin{Bmatrix}{1,} & {x > 0} \\{{- 1},} & {x < 0}\end{Bmatrix}.}$

Wherein, the hands-free call device further comprises a receiver endcomposed of at least one loudspeaker, and the method further comprises:

providing a virtual loudspeaker of one loudspeaker in the receiver endwith a connection line between the loudspeaker and its virtualloudspeaker directed to direction γ1, and defining a third collectionangle directed to a direction determined by the second collection angle.

According to another aspect of the present invention, an apparatus forimproving the call quality of a hands-free call device is provided,comprising:

a voice feature determination unit configured to scan within an initialfirst collection angle of a transmitter end; and after a voice featuresignal is scanned within the first collection angle, according to adirection of the voice feature signal, determine a second collectionangle smaller than the first collection angle within the firstcollection angle; and

a direction calibration unit configured to calibrate the transmitter endto a direction determined by the second collection angle.

Wherein, the apparatus further comprises: a virtual microphone creationunit configured to make a reverse extension line through the mainmicrophone in direction γ1 when a voice feature signal is scanned indirection γ1 within the initial first collection angle of thetransmitter end, draw a circle by taking the main microphone as a centerand a connection line between the main microphone and one of theauxiliary microphones as a radius, and determine intersection of an arcof the circle and the reverse extension line as a virtual microphone ofthe main microphone; and

an angle determination unit configured to take the main microphone andits virtual microphone as a new voice array, define an angle β1 smallerthan the first collection angle, and judge in real time whether a voicefeature signal is existed within the angle β1; if so, determine theangle β1 as a second collection angle; and if not, take the connectionline between the main microphone and one of the auxiliary microphones asan axis of symmetry, define a mirror angle β2 of the angle β1 withrespect to the axis of symmetry, and determine the angle β2 as a secondcollection angle.

Wherein, the angle determination unit is further configured to:

detect envelope energy of the voice feature signal in direction γ1, anddetect a zero-crossing rate of the voice feature signal in direction γ1when an energy detection value is larger than a first predeterminedthreshold; and

determine that a voice feature signal is existed in the angle β1, whenthe zero-crossing rate of the voice feature signal in direction γ1reaches a second predetermined threshold.

Wherein, the angle determination unit comprises:

an envelope detection unit configured to detect envelope energy of thevoice feature signal in direction γ1 through the following formula:

power=0;power=power*(1-alpha)+Σ_(n=1) ^(N) x(n)*x(n)

wherein, power is an energy value of the voice feature signal, parameteralpha is a weighted factor, and parameter N is a specific value of avoice feature signal at a time point; and

a zero-crossing detection unit configured to detect a zero-crossing rateof the voice feature signal in direction γ1 through the followingformula:

${Z\_ rate} = \left. {\frac{1}{2}\sum\limits_{m = 0}^{N - 1}}\; \middle| {{sgn}\left\lbrack {{x(n)} - {{sgn}\left( {x\left( {n - 1} \right)} \right)}} \right\rbrack} \right.$

wherein, Z_rate is a zero-crossing rate of the voice feature signal, nis a value among a discrete time series, and

${{sgn}\lbrack x\rbrack} = {\begin{Bmatrix}{1,} & {x > 0} \\{{- 1},} & {x < 0}\end{Bmatrix}.}$

Wherein, the apparatus further comprises a receiver end location unitconfigured to provide a virtual loudspeaker of one loudspeaker in thereceiver end with a connection line between the loudspeaker and itsvirtual loudspeaker directed to direction γ1, and define a thirdcollection angle having a regional extent covering a directiondetermined by the second collection angle.

According to another aspect of the present invention, a hands-free calldevice is provided, comprising a transmitter end composed of a mainmicrophone and at least one auxiliary microphone, a receiver endcomposed of at least one loudspeaker, and the aforementioned apparatusfor improving the call quality of the hands-free call device.

By performing a voice calibration location of the transmitter end, themethod and apparatus for improving the call quality of a hands-free calldevice of the present invention narrow the voice pickup angle of thetransmitter end into a relatively accurate range, thereby avoiding thevoice signal to noise ratio from being influenced by much ambient noisein the voice signal picked up by the transmitter end, solving theproblem that the call quality of the hands-free call device is not high,and improving the call quality of the hands-free call device.

Other characteristics and advantages of the present application will beelaborated in the subsequent Description, and they are partly obviousfrom the Description or acquirable by implementing the presentapplication. The objective and other advantages of the presentapplication can be realized and achieved through the structuresparticularly pointed out in the Description, claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings are provided for further understanding of the presentinvention, and constitute a part of the Description to explain thepresent invention together with the embodiments of the presentinvention, rather than restricting the present invention. In which,

FIG. 1 is a flowchart of a method for improving the call quality of ahands-free call device provided by one embodiment of the presentinvention;

FIG. 2 is a principle diagram of a method for improving the call qualityof a hands-free call device provided by one embodiment of the presentinvention;

FIG. 3a is a first schematic diagram of a transmitter end calibrationprovided by one embodiment of the present invention;

FIG. 3b is a second schematic diagram of a transmitter end calibrationprovided by one embodiment of the present invention;

FIG. 4 is flowchart of determination of a voice feature signal providedby one embodiment of the present invention;

FIG. 5 is a schematic diagram of a receiver end calibration provided byone embodiment of the present invention; and

FIG. 6 is a block diagram of an apparatus for improving the call qualityof a hands-free call device provided by one embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The core idea of the present invention is to track the direction of avoice source in real time through a sound source localization technologyfor microphone array, and at the same time, to determine a voiceprotection angle smaller than an initial voice protection angle toperform a voice pickup, so that the interference from surroundingambient noise can be greatly reduced to achieve the purpose of improvinga transmission signal to noise ratio. Meanwhile, a directionalcompensation is made for the loudspeaker array using orientationinformation of the voice source, so that the produced sound is justdirected to the voice source, thereby improving the privacy ofreception.

FIG. 1 is a flowchart of a method for improving the call quality of ahands-free call device provided by one embodiment of the presentinvention. Referring to FIG. 1, the hands-free call device comprises atransmitter end composed of a main microphone and at least one auxiliarymicrophone, and the method comprises:

step S110: scanning within an initial first collection angle of thetransmitter end;

step S120: after a voice feature signal is scanned within the firstcollection angle, according to a direction of the voice feature signal,determining a second collection angle smaller than the first collectionangle within the first collection angle; and

step S130: calibrating the transmitter end to a direction determined bythe second collection angle.

Through those steps, the voice protection angle of the transmitter endis narrowed to a smaller angle, and a voice pickup is conducted withinthe newly determined smaller angle, so that the interference on thevoice signal from ambient noise can be avoided to improve thetransmission signal to noise ratio, thereby improving the call qualityof the hands-free call device.

FIG. 2 is principle diagram of a method for improving the call qualityof a hands-free call device provided by one embodiment of the presentinvention. Referring to FIG. 2, the hands-free call device 1 comprises:a transmitter end and a receiver end;

the transmitter end comprises a main microphone MIC-a and an auxiliarymicrophone MIC-b, and the receiver end comprises a main loudspeakerSPK-a and an auxiliary loudspeaker SPK-b;

an angle α is an initial scanning angle of the transmitter end; during anormal communication, the transmitter end collects a signal, i.e., itfirstly scans within a larger collection angle α, and after a voicefeature signal is detected within the angle α, it narrows the collectionangle to an angle β to achieve the purpose of voice location at thetransmitter end. The process of voice location at the transmitter end isthat the transmitter end scans a voice feature signal within an initialscanning angle α, and when a voice feature signal is determined as beingexisted within an angle β, the transmitter end is located to a directiondetermined by the angle, i.e., a position or orientation where the userspeaks (as shown in FIG. 2, the range of the angle β just covers theposition of a head, and the location of the head is more accurate thanthat made by the angle α). The function of the method of the presentinvention is to narrow the initial scanning angle to a smaller secondcollection angle β. Thus the voice protection angle becomes smaller, andthe position where a user speaks can be located more accurately, therebyreducing the ambient noise in the voice signal and improving the voicequality.

FIG. 3a is a first schematic diagram of a transmitter end calibrationprovided by one embodiment of the present invention. Referring to FIG.3a , among the reference signs, 1 denotes a hands-free call device, 2denotes an auxiliary loudspeaker, 3 denotes an auxiliary microphone, and4 denotes a virtual microphone of a main microphone.

An improvement of the hands-free call device of the present invention isimplemented as follows:

referring to FIG. 3a , during a communication, firstly a voice scan ismade by the transmitter end within a larger first collection angle α,and when a voice feature signal is scanned in direction γ1 within thefirst collection angle α, a virtual microphone MIC-c is provided in areverse extension line of the main microphone MIC-a from direction γ1,so as to be located on an arc which takes the main microphone MIC-a as acenter and a connection line between the main microphone MIC-a and theauxiliary microphone MIC-b as a radius. Next, the main microphone MIC-aand the virtual microphone MIC-c constitute a new array, and adirectional angle of the new array is defined as a very small secondcollection angle β1 directed to a small range in direction γ1, and thevalue of β1 is specifically selected according to different applicationscenarios.

Since the auxiliary array element is absent, with respect to an arraycomposed of two dot array elements (MIC-a and MIC-c), it is difficult todistinguish whether a voice comes from the left side (γ1) or the rightside (γ2) of a connection between the main microphone MIC-a and theauxiliary microphone MIC-b. One of the core ideas of the method providedby the present invention is to judge using the virtual microphone MIC-c.The judgment method firstly provides a virtual microphone MIC-c indirection γ1 as shown in FIG. 3a and forms a directional angle β1, so asto judge any voice feature signal within the directional angle β1 inreal time; if a voice feature signal is found, the directional angle β1is determined as a second collection angle of the transmitter end, andthe transmitter end is calibrated to a direction determined by thesecond collection angle (β1). If no voice feature signal is found, avirtual microphone MIC-c is immediately provided anew at an oppositemirror side of the connection line between the main microphone MIC-a andthe auxiliary microphone MIC-b, so as to judge the direction of thevoice.

FIG. 3b is a second schematic diagram of a transmitter end calibrationprovided by one embodiment of the present invention. Referring to FIG.3b , among the reference signs, 1 denotes a hands-free call device, 2denotes an auxiliary loudspeaker, 3 denotes an auxiliary microphone, and4 denotes a virtual microphone of a main microphone.

If no voice feature signal is found within the directional angle β1 asshown in FIG. 3a , a symmetrical angle β2 of β1 is provided at the otherside of the connection between the main microphone MIC-a and theauxiliary microphone MIC-b as shown in FIG. 3b , and when a voicefeature signal is determined as being existed within the angle β2, thetransmitter end is calibrated to a direction determined by β2. Throughthe above steps, the location and calibration of the transmitter end arecompleted to improve the directivity of voice pickup.

Next, the location of the transmitter end is specifically described inconjunction with the judgment of the voice feature signal.

FIG. 4 is a flowchart of determination of a voice feature signalprovided by one embodiment of the present invention. Referring to FIG.4, specifically judging in real time whether any voice feature signal isexisted within the angle β1 comprises:

1. collecting a signal, wherein the collected signal is a scanned voicefeature signal in direction γ1;

2. detecting envelope energy of the voice feature signal, and judgingwhether the energy value is larger than a first predetermined threshold;if so, detecting a zero-crossing rate of the voice feature signal; andif not, returning to determine a direction of the voice feature signalagain and a voice feature signal;

3. judging a zero-crossing rate of the voice feature signal; when thezero-crossing rate is larger than a second predetermined threshold,determining that a voice feature signal is existed within the collectionangle β1; taking the directional angle β1 as a smaller second collectionangle, so as to calibrate the transmitter end according to the secondcollection angle.

In this embodiment, detecting envelope energy of the voice featuresignal in direction γ1 comprises:

detecting envelope energy through the following formula:

power=0;power=power*(1-alpha)+Σ_(n=1) ^(N) x(n)*x(n)

wherein, power is an energy value of the voice feature signal, parameteralpha is a weighted factor, and parameter N is a specific value of voicefeature signal at a time point; wherein the detection sensitivity iscontrolled by adjusting the two parameters alpha and N, so as to ensurestability of the envelope energy detection. Once the envelope energypower is found to be larger than the first predetermined threshold (setupon actual conditions), the step of detecting the zero-crossing rate isperformed.

Detecting the zero-crossing rate of the voice feature signal indirection γ1 comprises: detecting the zero-crossing rate through thefollowing formula:

${Z\_ rate} = \left. {\frac{1}{2}\sum\limits_{m = 0}^{N - 1}}\; \middle| {{sgn}\left\lbrack {{x(n)} - {{sgn}\left( {x\left( {n - 1} \right)} \right)}} \right\rbrack} \right.$

wherein, Z_rate is a zero-crossing rate of the voice feature signal, nis a value among a discrete time series, and

${{sgn}\lbrack x\rbrack} = {\begin{Bmatrix}{1,} & {x > 0} \\{{- 1},} & {x < 0}\end{Bmatrix}.}$

When the zero-crossing rate Z_rate is larger than the secondpredetermined threshold, it is deemed that the collected signals withinthe angle β1 contain a voice feature signal, and a voice action isdetermined.

After judging that a voice feature signal is existed within the angleβ1, the transmitter end is located and calibrated to a range determinedby the angle β1. If there is no voice feature signal within the angle β1(γ1 is not a voice source direction), it is judged whether there is anyvoice feature signal within an angle β2 symmetrical to β1 about theconnection line between MIC-a and MIC-b. At that time, an envelopeenergy detection and a zero-crossing rate detection may be performed tofurther verify the voice feature signal within β2.

In conclusion, an accurate location of the transmitter end is achievedby the location of the virtual array element and the detection of thevoice feature signal.

FIG. 5 is a schematic diagram of a receiver end calibration provided byone embodiment of the present invention. Among the reference signs, 1denotes a hands-free call device, 2 denotes an auxiliary loudspeaker,and 3 denotes a main microphone.

After the transmitter end is located, a directional compensation is madefor the loudspeaker array using orientation information of the voicesource, so that the produced sound is just directed to the voice source,i.e., a sound producing direction of the loudspeaker array is adjusted,so far as possible, to a position where the user speaks located by thetransmitter end, i.e., a direction determined by the second collectionangle, thereby improving the privacy of reception. Specifically, aloudspeaker SPK-b is virtualized using a virtual array elementtechnology, and a connection line between a virtual loudspeaker SPK-cand a loudspeaker SPK-a is directed to the voice direction. Next, adirectional angle is provided so that a coverage area of the thirdcollection angle (i.e., a regional extent of sound propagation includedby the third collection angle) covers a voice direction determined bythe second collection angle (as shown in FIG. 5, the angle range belowSPK-a covers the position of the head). Preferably, the third collectionangle is directly directed to a voice direction determined by the secondcollection angle.

Referring to FIG. 5, the hands-free call device further comprises areceiver end composed of at least one loudspeaker. After a calibrationof the transmitter end is completed by determining the second collectionangle and direction, the method further comprises calibrating thereceiver end of the hands-free call device, providing a virtualloudspeaker of one loudspeaker in the receiver end with the connectionline between the loudspeaker and its virtual loudspeaker directed todirection γ1, and defining a third collection angle directed to adirection determined by the second collection angle. The thirdcollection angle is actually an angle range of sound playing, includingthe second collection angle and direction, so that the loudspeaker playstowards the orientation of the voice source as much as possible, therebyreducing the voice playing range and improving the privacy of reception.

During usage of the hands-free call device, since a distance between themicrophone and the loudspeaker is short, the receiver end may becalibrated in a direction of the voice feature signal determined duringthe calibration of the transmitter end.

Referring to FIG. 5, a virtual loudspeaker SPK-c of the auxiliaryloudspeaker SPK-b is provided in a reverse extension line of the mainloudspeaker SPK-a from direction γ1, so as to be located on an arc whichtakes the main loudspeaker SPK-a as a center and a connection linebetween the main loudspeaker SPK-a and the auxiliary loudspeaker SPK-bas a radius. The main loudspeaker SPK-a and the virtual loudspeakerSPK-c constitute a new array, and a directional angle of the new arrayis defined as a third collection angle directed to a directiondetermined by the second collection angle, which is determined duringcalibration of the transmitter end, so as to complete the location andcalibration of the receiver end.

It shall be appreciated that those angles occurring in FIGS. 3a, 3b and5 are for the purpose of exemplarily describing the angle ranges forlocating the transmitter end and the receiver end, and the angulardimensions are not actual. The embodiments of the present inventionimprove the signal to noise ratio of the hands-free voice signal bylocating and calibrating the transmitter end, and improve the privacy ofreception by locating the receiver end.

In conclusion, by calibrating the transmitter end and the receiver end,the method for improving the call quality of the hands-free call deviceof the present invention reduces the interference from ambient noise,improves the transmission signal to noise ratio, and achieves thepurpose of improving the call quality of the hands-free call device. Inaddition, it performs a direction compensation for the loudspeakerarray, so that the produced sound is just directed to the voice source,thereby improving the privacy of reception and the user experience. Themethod can be applied to a smart device having the hands-free callfunction, such as a smart watch, and greatly improves the callperformance of the smart device.

According to another aspect of the present invention, an apparatus forimproving the call quality of a hands-free call device is provided. FIG.6 is a block diagram of an apparatus for improving the call quality of ahands-free call device provided by one embodiment of the presentinvention, wherein the apparatus 600 comprises:

a voice feature determination unit 601 configured to scan within aninitial first collection angle of a transmitter end; and after a voicefeature signal is scanned within the first collection angle, accordingto a direction of the voice feature signal, determine a secondcollection angle smaller than the first collection angle within thefirst collection angle; and

a direction calibration unit 602 configured to calibrate the transmitterend to a direction determined by the second collection angle.

Wherein, the apparatus further comprises a virtual microphone creationunit configured to make a reverse extension line through the mainmicrophone in direction γ1 when a voice feature signal is scanned indirection γ1 within the initial first collection angle of thetransmitter end, draw a circle by taking the main microphone as a centerand a connection line between the main microphone and one of theauxiliary microphones as a radius, and determine intersection of an arcof the circle and the reverse extension line as a virtual microphone ofthe main microphone; and

an angle determination unit configured to take the main microphone andits virtual microphone as a new voice array, define an angle β1 smallerthan the first collection angle, and judge in real time whether a voicefeature signal is existed within the angle β1; if so, determine thatangle β1 as a second collection angle; and if not, take a connectionline between the main microphone and one of the auxiliary microphones asan axis of symmetry, define a mirror angle β2 of the angle β1 withrespect to the axis of symmetry, and determine the angle β2 as a secondcollection angle.

Wherein, the angle determination unit is further configured to,

detect envelope energy of the voice feature signal in direction γ1, anddetect a zero-crossing rate of the voice feature signal in direction γ1when the energy detection value is larger than a first predeterminedthreshold;

determine that a voice feature signal is existed in the angle β1, whenthe zero-crossing rate of the voice feature signal in direction γ1reaches a second predetermined threshold.

Wherein, the angle determination unit comprises:

an envelope detection unit configured to detect envelope energy of thevoice feature signal in direction γ1 through the following formula:

power=0;power=power*(1-alpha)+Σ_(n=1) ^(N) x(n)*x(n)

wherein, power is an energy value of the voice feature signal, parameteralpha is a weighted factor, and N is a specific value of the voicefeature signal at a time point;

a zero-crossing detection unit configured to detect a zero-crossing rateof the voice feature signal in direction γ1 through the followingformula:

${Z\_ rate} = \left. {\frac{1}{2}\sum\limits_{m = 0}^{N - 1}}\; \middle| {{sgn}\left\lbrack {{x(n)} - {{sgn}\left( {x\left( {n - 1} \right)} \right)}} \right\rbrack} \right.$

wherein, Z_rate is a zero-crossing rate of the voice feature signal, nis a value among a discrete time series, and

${{sgn}\lbrack x\rbrack} = {\begin{Bmatrix}{1,} & {x > 0} \\{{- 1},} & {x < 0}\end{Bmatrix}.}$

Wherein, the apparatus further comprises a receiver end location unitconfigured to provide a virtual loudspeaker of one loudspeaker in thereceiver end with a connection line between the loudspeaker and itsvirtual loudspeaker directed to direction γ1, and define a thirdcollection angle having a regional extent covering a directiondetermined by the second collection angle.

According to another aspect of the present invention, a hands-free calldevice is provided, comprising a transmitter end composed of a mainmicrophone and at least one auxiliary microphone, a receiver endcomposed of at least one loudspeaker, and the aforementioned apparatusfor improving the call quality of the hands-free call device.

To be noted, the transmitter end and the receiver end of the hands-freecall device of the present invention can be improved in theaforementioned method for improving the hands-free call quality. Butunder some application scenarios, the hands-free call device onlycomprises a transmitter end or a receiver end. In that case, thereceiver end may be improved in the method for improving the hands-freecall quality at the receiver end in the embodiment of the presentinvention, or the transmitter end may be improved in the method forimproving the hands-free call quality at the transmitter end in theembodiment of the present invention. That is to say, the method forimproving the hands-free call quality at the receiver end and at thetransmitter end in the present invention can be implemented separately,which are omitted herein.

The above descriptions are just preferred embodiments of the presentinvention, rather than restrictions to the protection scope of thepresent invention. Any amendment, equivalent replacement, improvement,etc. made within the spirit and principle of the present invention shallfall within the protection scope of the present invention.

1. A method for improving the call quality of a hands-free call devicethat comprises a transmitter end composed of a main microphone and atleast one auxiliary microphone, wherein the method comprises: scanning avoice feature signal within an initial first collection angle of thetransmitter end; after a voice feature signal is scanned within thefirst collection angle, according to a direction of the voice featuresignal, determining a second collection angle smaller than the firstcollection angle within the first collection angle; and calibrating thetransmitter end to a direction determined by the second collectionangle; wherein after a voice feature signal is scanned within the firstcollection angle, according to a direction of the voice feature signal,determining a second collection angle smaller than the first collectionangle within the first collection angle comprises: making a reverseextension line through the main microphone in direction γ1 when a voicefeature signal is scanned in direction γ1 within the initial firstcollection angle of the transmitter end, drawing a circle by taking themain microphone as a center and a connection line between the mainmicrophone and one of the auxiliary microphones as a radius, anddetermining intersection of an arc of the circle and the reverseextension line as a virtual microphone of the main microphone; takingthe main microphone and its virtual microphone as a new voice array,defining an angle β1 smaller than the first collection angle, andjudging in real time whether a voice feature signal is existed withinthe angle β1; if so, determining the angle β1 as a second collectionangle; and if not, taking the connection line between the mainmicrophone and one of the auxiliary microphones as an axis of symmetry,defining a mirror angle β2 of the angle β1 with respect to the axis ofsymmetry, and determining the angle β2 as a second collection angle. 2.(canceled)
 3. The method according to claim 1, wherein judging in realtime whether a voice feature signal is existed within the angle β1comprises: detecting envelope energy of the voice feature signal indirection γ1, and detecting a zero-crossing rate of the voice featuresignal in direction γ1 when an energy detection value is larger than afirst predetermined threshold; and determining that a voice featuresignal is existed in the angle β1, when the zero-crossing rate of thevoice feature signal in direction γ1 reaches a second predeterminedthreshold.
 4. The method according to claim 3, wherein detectingenvelope energy of the voice feature signal in direction γ1 comprises:detecting envelope energy through the following formula:power=0;power=power*(1-alpha)+Σ_(n=1) ^(N) x(n)*x(n) wherein, power isan energy value of the voice feature signal, parameter alpha is aweighted factor, and parameter N is a specific value of voice featuresignal at a time point; detecting a zero-crossing rate of the voicefeature signal in direction γ1 comprises: detecting a zero-crossing ratethrough the following formula:${Z\_ rate} = \left. {\frac{1}{2}\sum\limits_{m = 0}^{N - 1}}\; \middle| {{sgn}\left\lbrack {{x(n)} - {{sgn}\left( {x\left( {n - 1} \right)} \right)}} \right\rbrack} \right.$wherein, Z_rate is a zero-crossing rate of the voice feature signal, nis a value among a discrete time series, and${{sgn}\lbrack x\rbrack} = {\begin{Bmatrix}{1,} & {x > 0} \\{{- 1},} & {x < 0}\end{Bmatrix}.}$
 5. The method according to claim 1, wherein thehands-free call device further comprises a receiver end composed of atleast one loudspeaker, and wherein the method further comprises:providing a virtual loudspeaker of one loudspeaker in the receiver endwith a connection line between the loudspeaker and its virtualloudspeaker directed to direction γ1, and defining a third collectionangle having a regional extent covering a direction determined by thesecond collection angle.
 6. An apparatus for improving the call qualityof a hands-free call device that comprises a transmitter end composed ofa main microphone and at least one auxiliary microphone, comprising: avoice feature determination unit configured to scan a voice featuresignal within an initial first collection angle of a transmitter end;and after a voice feature signal is scanned within the first collectionangle, according to a direction of the voice feature signal, determine asecond collection angle smaller than the first collection angle withinthe first collection angle; and a direction calibration unit configuredto calibrate the transmitter end to a direction determined by the secondcollection angle; wherein the voice feature determination unitcomprising: a virtual microphone creation unit configured to make areverse extension line through the main microphone in direction γ1 whena voice feature signal is scanned in direction γ1 within the initialfirst collection angle of the transmitter end, draw a circle by takingthe main microphone as a center and a connection line between the mainmicrophone and one of the auxiliary microphones as a radius, anddetermine intersection of an arc of the circle and the reverse extensionline as a virtual microphone of the main microphone; and an angledetermination unit configured to take the main microphone and itsvirtual microphone as a new voice array, define an angle β1 smaller thanthe first collection angle, and judge in real time whether a voicefeature signal is existed within the angle β1; if so, determine theangle β1 as a second collection angle; and if not, take the connectionline between the main microphone and one of the auxiliary microphones asan axis of symmetry, define a mirror angle β2 of the angle β1 withrespect to the axis of symmetry, and determine the angle β2 as a secondcollection angle.
 7. (canceled)
 8. The apparatus according to claim 6,wherein the angle determination unit is further configured to: detectenvelope energy of the voice feature signal in direction γ1, and detecta zero-crossing rate of the voice feature signal in direction γ1 when anenergy detection value is larger than a first predetermined threshold;and determine that a voice feature signal is existed in the angle β1,when the zero-crossing rate of the voice feature signal in direction γ1reaches a second predetermined threshold; the angle determination unitcomprises: an envelope detection unit configured to detect envelopeenergy of the voice feature signal in direction γ1 through the followingformula:power=0;power=power*(1-alpha)+Σ_(n=1) ^(N) x(n)*x(n) wherein, power isan energy value of the voice feature signal, parameter alpha is aweighted factor, and parameter N is a specific value of a voice featuresignal at a time point; and a zero-crossing detection unit configured todetect a zero-crossing rate of the voice feature signal in direction γ1through the following formula:${Z\_ rate} = \left. {\frac{1}{2}\sum\limits_{m = 0}^{N - 1}}\; \middle| {{sgn}\left\lbrack {{x(n)} - {{sgn}\left( {x\left( {n - 1} \right)} \right)}} \right\rbrack} \right.$wherein, Z_rate is a zero-crossing rate of the voice feature signal, nis a value among a discrete time series, and${{sgn}\lbrack x\rbrack} = {\begin{Bmatrix}{1,} & {x > 0} \\{{- 1},} & {x < 0}\end{Bmatrix}.}$
 9. The apparatus according to claim 6, wherein thehands-free call device further comprises a receiver end composed of atleast one loudspeaker, and wherein the apparatus further comprising: areceiver end location unit configured to provide a virtual loudspeakerof one loudspeaker in the receiver end with a connection line betweenthe loudspeaker and its virtual loudspeaker directed to direction γ1,and define a third collection angle having a regional extent covering adirection determined by the second collection angle.
 10. A hands-freecall device, comprising a transmitter end composed of a main microphoneand at least one auxiliary microphone, a receiver end composed of atleast one loudspeaker, and the apparatus according to claim 6.